Browsing by Subject "Ultrasound"

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  • Lampsijärvi, Eetu (Helsingin yliopisto, 2020)
    The feasibility of quantitatively measuring ultrasound in air with a Schlieren arrangement has been demonstrated before, but previous work demonstrating calibration of the system combined with computation to yield the 3D pressure field does not exist. The present work demonstrates the feasibility of this both in theory and practice, and characterizes the setup used to gain the results. Elementary ray optical and Schlieren theory is exhibited to support the claims. Derivation of ray optical equations related to quantitative Schlieren measurements are shown step by step to help understand the basics. A numerical example based on the theoretical results is then displayed: Synthetic Schlieren images are computed for a theoretical ultrasonic field using direct numerical integration, then the ultrasonic field is recovered from the Synthetic Schlieren images using the inverse Abel transform. Accuracy of the inverse transform is evaluated in presence of synthetic noise. The Schlieren arrangement, including the optics, optomechanics, and electronics, to produce the results is explained along with the stroboscopic use of the light source to freeze ultrasound in the photographs. Postprocessing methods such as background subtraction and median and Gaussian filtering are used. The repeatability and uncertainty of the calibration is examined by performing repeated calibration while translating or rotating the calibration targets. The ultrasound fields emitted by three transducers (100 kHz, 175 kHz, and 300 kHz) when driven by 5 cycle sine bursts at 400 Vpp are measured at two different points in time. The measured 3D pressure fields measured for each transducer are shown along with a line profile near the acoustic axis. Pressure amplitudes range near 1 kPa, which is near the acoustic pressure, are seen. Nonlinearity is seen in the waveforms as expected for such high pressures. Noise estimates from the numerical example suggest that the pressure amplitudes have an uncertainty of 10% due to noise in the photographs. Calibration experiments suggest that additional uncertainty of about 2% per degree of freedom (Z, X, rotation) is to be expected unless especial care is taken. The worst-case uncertainty is estimated to be 18%. Limitations and advantages of the method are discussed. As Schlieren is a non-contacting method it is advantageous over microphone measurements, which may affect the field they are measuring. As every photograph measures the whole field, no scanning of the measurement device is required, such as with a microphone or with an LDV. Suggestions to improve the measurement setup are provided.
  • Nieminen, Heikki J.; Ylitalo, Tuomo; Suuronen, Jussi-Petteri; Rahunen, Krista; Salmi, Ari; Saarakkala, Simo; Serimaa, Ritva; Haeggstrom, Edward (2015)
    There is no cure for osteoarthritis. Current drug delivery relies on systemic delivery or injections into the joint. Because articular cartilage (AC) degeneration can be local and drug exposure outside the lesion can cause adverse effects, localized drug delivery could permit new drug treatment strategies. We investigated whether intense megahertz ultrasound (frequency: 1.138 MHz, peak positive pressure: 2.7 MPa, I-spta: 5 W/cm(2), beam width: 5.7 mm at -6 dB, duty cycle: 5%, pulse repetition frequency: 285 Hz, mechanical index: 1.1) can deliver agents into AC without damaging it. Using ultrasound, we delivered a drug surrogate down to a depth corresponding to 53% depth of the AC thickness without causing histologically detectable damage to the AC. This may be important because early osteoarthritis typically exhibits histopathologic changes in the superficial AC. In conclusion, we identify intense megahertz ultrasound as a technique that potentially enables localized non-destructive delivery of osteoarthritis drugs or drug carriers into articular cartilage. (E-mail: heikki.nieminen@helsinki.fi) (C) 2015 World Federation for Ultrasound in Medicine & Biology.
  • Yki-Jarvinen, Hannele (2016)
    Non-alcoholic fatty liver disease (NAFLD) increases risk of mortality from liver and cardiovascular disease (CVD) and is the major cause of hepatocellular carcinoma (HCC), which may develop without cirrhosis. NAFLD predicts type 2 diabetes, even independently of obesity. Globally, the prevalence of NAFLD averages 25% and is as common as the metabolic syndrome. The majority of patients with type 2 diabetes have NAFLD. The challenge for the diabetologist is to identify patients at risk of advanced liver disease and HCC. At a minimum, liver function tests (LFTs), despite being neither specific nor sensitive, should be performed in all patients with the metabolic syndrome or type 2 diabetes. Increases in LFTs, for which the updated reference values are lower (serum ALT approximate to 30 U/l in men and approximate to 20 U/l in women) than those hitherto used in many laboratories, should prompt assessment of fibrosis biomarkers and referral of individuals at risk to a NAFLD/hepatology clinic. Preferably, evaluation of NAFLD should be based on measurement of steatosis biomarkers or ultrasound if easily available. A large number of individuals carry the patatin-like phospholipase domain containing 3 (PNPLA3) I148M variant (30-50%) or the transmembrane 6 superfamily member 2 (TM6SF2) E167K variant (11-15%). These variants increase the risk of advanced liver disease and HCC but not of diabetes or CVD. Genotyping of selected patients for these variants is recommended. Many patients have 'double trouble', i.e. carry both a genetic risk factor and have the metabolic syndrome. Excess use of alcohol could be a cause of 'triple trouble', but such patients would be classified as having alcoholic fatty liver disease. This review summarises a presentation given at the symposium 'The liver in focus' at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Kenneth Cusi, DOI: 10.1007/s00125-016-3952-1, and by John Jones, DOI: 10.1007/s00125-016-3940-5) and a commentary by the Session Chair, Michael Roden (DOI: 10.1007/s00125-016-3911-x).
  • Alanne, Leena; Bhide, Amarnath; Hoffren, Jonna; Lantto, Juulia; Huhta, Heikki; Kokki, Merja; Haapsamo, Mervi; Acharya, Ganesh; Räsänen, Juha (2020)
    Introduction We hypothesized that nifedipine and sildenafil would have no detrimental effects on placental hemodynamics and gas exchange under fetal hypoxemia. Methods In 33 chronically instrumented fetal sheep, placental volume blood flow (QPlac) and umbilical artery (UA) vascular impedance were measured by Doppler ultrasonography. Fetal carotid artery blood pressure and blood gas values were monitored. After baseline data collection, maternal and fetal hypoxemia were induced. Following hypoxemia phase data collection, 12 fetuses received sildenafil and 9 fetuses nifedipine infusion, and 12 fetuses served as controls receiving saline infusion. Data were collected 30 and 120 min after infusion was started. Then maternal oxygenation was normalized and normoxemia phase data were collected, while infusion was continued. Results Hypoxemia significantly decreased fetal pO2 and blood pressure. In the sildenafil group at 30- and 120-min hypoxemia + infusion phases, fetal blood pressure and QPlac were significantly lower and pCO2 higher than at baseline without returning to baseline level at normoxemia + infusion phase. In hypoxemia, nifedipine did not affect fetal blood pressure or placental hemodynamics. Both in the sildenafil and nifedipine groups, fetal pO2 remained significantly lower at normoxemia + infusion phase than in the control group. Umbilical artery vascular impedance did not change during the experiment. Discussion In fetal hypoxemia, sildenafil had detrimental effects on placental hemodynamics that disturbed placental gas exchange. Nifedipine did not alter placental hemodynamics in hypoxemia but disturbed placental gas exchange upon returning to normoxemia. Umbilical artery vascular impedance did not reflect alterations in placental hemodynamics.
  • Tirri, Tomi (Helsingin yliopisto, 2017)
    Kuvantamista hyödyntävässä toimenpiteessä eli toimenpideradiologiassa on kliininen tarve määrittää potilaan tukos- tai vuototaipumusta. Ultraäänitoimenpiteissä vuotoriskiä ennakoidaan protrombiiniajan (PT) ja siitä johdetun International Ration (INR) avulla. Sydänpotilailla tukosriskiä pienennetään toimenpiteen aikana annostelemalla suonen- sisäisesti hepariinia, jolloin aktivoidulla hyytymisajalla (ACT) voidaan seurata hepariinin vaikutusta. Kannettavalla vierilaitteella voidaan verianalyysit suorittaa toimenpide- huoneessa,jolloin tulosviive pienenee. Tutkielmassa verifioitiin HUS-Kuvantamisen radiologian hankkima ITC Hemochron® Signature Elite-vierilaitteen kokoverianalyysit PT, INR ja aktivoitu partielli tromboplastiiniaika (APTT) vertaamalla laitteen antamia tuloksia laboratorion veriplasmaa käyttäviin analyysituloksiin. Laitteen aktivoidun hyytymisajan (ACT LR ja ACT+) tuloksia verrattiin laboratorion antifaktori X-aktiivisuuteen (anti-FXa). Tavoitteena oli selvittää potilasaineiston avulla soveltuuko ITC Hemochron® Signature Elite-vierilaite kliiniseen käyttöön toimenpideradiologiassa. Ultraäänitoimenpiteissä potilaita oli yhteensä 20 ja sydänpotilaita oli 15. Potilaita ei valikoitu vaan kaikki näyt- teiden keräyspäivinä tammikuussa ja huhtikuussa 2015 HUS-Kuvantaminen radiolo- giassa ulträäni- tai sydäntoimenpiteissä olleet potilaat otettiin mukaan. PT-mittauksissa ero laboratorion menetelmän ja Hemochron® Signature Elite PT:n välillä oli -5,5 sekuntia (-26,3 prosenttia) ja keskinäinen riippuvuus eli korrelaatio vähäinen (R=0,02). INR- mittauksissa ero oli 0,15 (15 prosenttia) ja korrelaatio vähäinen (R=0,1). APTT-mittauk- sissa ero oli 8,4 sekuntia (33,9 prosenttia) ja korrelaatio alhainen (R=0,33). ACT LR:lle ja ACT+:lle ei määritelty eroa, koska mittausasteikko eroaa laboratorion antiFXa:n kanssa. ACT LR:lle saatii korrelaatio oli 0,49 ja ja ACT+:lle 0,35.
  • Malinen, Henri (Helsingin yliopisto, 2021)
    Dendrite prevention can be achieved by manipulating the local chemical concentration gradient by ultrasound. An ultrasonic field, which generates acoustic streaming, can manipulate the ionic flux at the electrode surface by altering the local ion concentration gradient at said surface according to the streaming pattern. The pattern is determined by the ultrasonic field and the geometry of the sonication volume. The preventive action can be directed to an arbitrary point on the surface, or be swept across it to achieve a smoother electroplating. Dendritic growth is concentrated to areas of higher concentration gradient. This is because at the electrode surface both the electric and convective fluxes tend to zero. If the reduction of ions into their metallic form is fast enough, the metal layer growth rate is determined by the diffusive flux, which is determined by the ion concentration gradient and the diffusion constant of the ion in the electrolyte. In this study, tin was used as the transported ion instead of lithium for safety reasons. A custom-made battery mockup cell was constructed for the experiments. The anode was imaged with a usb microscope camera to determine the growth of the dendrites during the process. The electroplating current and piezo driving power were varied between 100 mA to 275 mA and 0 to 6.6 W, respectively. With piezo driving electrical power less than 10 W, it was possible to lower the maximum lengths of dendrites. Finite element method simulations were conducted to validate the hypothesis and experimental results. This ultrasonic method could be used to allow rechargeable, lightweight, high capacity lithium metal batteries. The piezos could be integrated into battery chargers.
  • Lehikoinen, Anni; Orden, Maija-Riitta; Heinonen, Seppo Tapani; Voutilainen, Raimo (2016)
    AimMaternal alcohol abuse is poorly recognised and causes developmental problems. This study explored the foetal central nervous systems (CNS), head circumference and psychomotor development of children exposed to drugs or alcohol during pregnancy up to 2.5years of age. MethodsWe recruited 23 pregnant women referred to Kuopio University Hospital, Finland, by their family doctor because of drug or alcohol abuse, and 22 control mothers. Foetal CNS parameters were measured by three-dimensional ultrasonography at the mean gestational age of 20weeks and the Griffiths Mental Developmental Scales (GMDS), and anthropometric measurements were carried out at the mean ages of one and 2.5years. ResultsThe exposed foetuses had decreased biparietal and occipito-frontal distances and head circumferences, but unchanged cerebellar volume at 20weeks, and decreased head circumferences and length and height at birth, one and 2.5years of age. They scored lower than the controls on the GMDS general quotient and the hearing, language and locomotor subscales at 2.5years of age. ConclusionMaternal alcohol or drug exposure was associated with decreased head size from mid-pregnancy to childhood and reduced development at 2.5years. Foetal head circumference at mid-pregnancy was a useful indicator of substance abuse affecting theCNS.
  • Mäkelä, Mikko (Helsingin yliopisto, 2020)
    Ultrasonic transducers convert electric energy into mechanical energy at ultrasonic frequencies. High-power ultrasound is widely used in the industry and in laboratories e.g. in cleaning, sonochemistry and welding solutions. To be effective in these cases, a piezoelectric transducer must deliver maximal power to the medium. Most of these systems rely on having the power delivery maximized during long driving sequences where stable performance is critical. Power ultrasonic transducers are typically narrowband, featuring high Q-value, that are finely tuned to a specific resonance frequency. The resonance frequency can vary during driving due to temperature, mechanical loading and nonlinear effects. When the transducers resonance frequency changes, drastic changes in its impedance (resonance to anti-resonance) can lead quickly to damage or failure of the driving electronics or the transducers themselves. In this work we developed a multi-channel high-power ultrasonic system with a software-based resonance frequency tracking and driving frequency control. The implementation features a feedback loop to maximize power delivery during long driving sequences in an ultrasonic cleaning vessel. The achieved total real power increased from 6.5 kW to almost 10 kW in peak with our feedback loop. The feedback loop also protected the electronics and transducers from breaking due to heating and varying impedance.
  • Vitikainen, Anne-Mari; Peltonen, Juha I.; Vartiainen, Eija (2017)
    The importance of quality assurance (QA) in medical ultrasound (US) has been widely recognized and recommendations concerning technical QA have been published over the years. However, the demonstrated impact of a properly working QA protocol on clinical routine has been scarce. We investigated the transducer write-off causes for a 5-y period in a multi-unit radiology department with an annual average of 230 transducers in demanding diagnostic use. The transducer faults and the initial observers of the faults leading to transducer write-offs were traced and categorized. The most common cause of transducer write-off was an image uniformity problem or element failure. Mechanical faults or excessive leakage current and defects in the lens constituted smaller yet substantial shares. Our results suggest that a properly working routine QA program can detect majority of the faults before they are reported by users. (E-mail: juha.peltonen@hus.fi) (C) 2017 World Federation for Ultrasound in Medicine & Biology.
  • Fromm, Annette; Thomassen, Lars; Naess, Halvor; Meijer, Rudy; Eide, Geir Egil; Krakenes, Jostein; Vedeler, Christian A.; Gerdts, Eva; Larsen, Terje H.; Kuiper, Karel K-J; Laxdal, Elin; Russell, David; Tatlisumak, Turgut; Waje-Andreassen, Ulrike (2013)
  • Nocera, Irene; Aliboni, Benedetta; Sgorbini, Micaela; Gracia-Calvo, Luis Alfonso; Conte, Giuseppe; Ben David, Liri; Citi, Simonetta (2020)
    Ultrasound (US) is a well-established technique for investigating joint diseases in horses, complementary to radiography. Few studies have been performed on the ultrasonographic aspect of the elbow joint in horses and no reports are available on donkeys. The aim of this study is to describe the ultrasonographic appearance of the elbow joint in healthy donkeys. Descriptive cohort study included 34 elbow joints, which were evaluated in 17 donkeys. Inclusion criteria included no lameness or musculoskeletal diseases in the donkeys. The structures evaluated were the lateral and medial collateral ligaments, ulnaris lateralis proximal tendon, distal biceps brachii tendon, triceps brachii tendon, and the articular space. For each structure, one good-quality image was recorded. The structures were retrospectively assessed for echogenicity, fiber orientation, bone appearance, and shape. The prevalence of the visualized structures was calculated. Cohen kappa coefficient was calculated for the repeatability (intraoperator agreement), the reproducibility (interoperator agreement), and the influence of the operator's experience in US examination. The US appearance of the structures was described. Statistical analysis showed scarce-to-moderate agreement concerning the repeatability and mostly scarce-to-good agreement concerning the reproducibility of the US examination; finally, low-to-discrete agreement concerning the operator's experience. Technical difficulties precluded an accurate description of the medial collateral ligament. The healthy animals included were limited. The US examination of the elbow joint in donkeys were similar to the features reported in horses. Individual experience partially influences the execution and the assessment of the US images. (C) 2020 The Author(s). Published by Elsevier Inc.
  • Rousou, Charis; Schuurmans, Carl C.L.; Urtti, Arto; Mastrobattista, Enrico; Storm, Gert; Moonen, Chrit; Kaarniranta, Kai; Deckers, Roel (2021)
    The unique anatomy of the eye and the presence of various biological barriers make efficacious ocular drug delivery challenging, particularly in the treatment of posterior eye diseases. This review focuses on the combination of ultrasound and microbubbles (USMB) as a minimally invasive method to improve the efficacy and targeting of ocular drug delivery. An extensive overview is given of the in vitro and in vivo studies investigating the mechanical effects of ultrasound-driven microbubbles aiming to: (i) temporarily disrupt the blood–retina barrier in order to enhance the delivery of systemically administered drugs into the eye, (ii) induce intracellular uptake of anticancer drugs and macromolecules and (iii) achieve targeted delivery of genes, for the treatment of ocular malignancies and degenerative diseases. Finally, the safety and tolerability aspects of USMB, essential for the translation of USMB to the clinic, are discussed.